A straightforward sequence to alkyl 1H-pyrrole-2,5-dicarboxylates starting from acylhydrazono esters and alkyl 2-aroyl-1-chlorocyclopropanecarboxylates

Abstract

A highly regioselective domino reaction was developed between alkyl 2-aroyl-1-chlorocyclopropanecarboxylates 1 and acylhydrazono esters 2 in the presence of Cs₂CO₃ under mild basic conditions, which directly afforded 2,3,5-trifunctionalized pyrroles in good to excellent yields with the extrusion of benzamide. A plausible pathway was proposed involving 1,2-elimination, regioselective nucleophilic addition, the intramolecular Mannich reaction, and the removal of benzamide to rationalize the formation of the aromatic pyrrole system.